IZw18 is among the most metal-poor (12+log(O/H)= 7.11 \(\sim \)  3\(\%\) 
solarAssuming a solar metallicity 12+log(O/H)\(_{\odot }\)  =
8.69 (Asplund et al. 2009); e.g., Kehrig et al. 2016, K16) Heii-emitting SF galaxies known at z \(\sim \)  0. It thus can
be considered a nearby analog of distant metal-poor Heii
emitters, providing a unique laboratory to study the high-ionization
phenomenon expected to be common in the reionization era. Based on
integral field spectroscopy (IFS) data, [1]}
unveiled the entire nebular Heii\(\lambda \) 4686-emitting region in
IZw18 with a diameter of \(\approx \) 5\(^{\prime \prime }\)  (\(\approx \)  440 pc
at the distance of 18.2 Mpc; Aloisi et al. 2007). K15 found that only
peculiar hot (nearly) metal-free massive stars could explain the
Heii ionization in IZw18 [2]}.
The main goal of this Letter is to investigate in detail the spatial correlation between the Heii
emission in IZw18 and its single HMXB [3]},
the variability of the latter on short (days) and long (decades)
timescales and its expected He\(^+\)  ionizing photon production to assess the contribution of the X-ray emission to the
nebular Heii\(\lambda \) 4686 ionization.
<TABLE>